What is the glass transition temperature Tg of a polymer?

What is the glass transition temperature Tg of a polymer?

The glass transition temperature is the temperature range where the polymer substrate changes from a rigid glassy material to a soft (not melted) material, and is usually measured in terms of the stiffness, or modulus.

How do you determine the glass transition temperature of a polymer?

There are three general techniques for measuring Tg:

1. Differential Scanning Calorimetry (DSC) – This is probably the most traditional and common technique for most polymeric materials.
2. Thermal Mechanical Analysis (TMA) – TMA is used to measure Coefficient of Thermal Expansion (CTE) of polymers.

What material type has a glass transition temperature Tg )?

amorphous PLA

What happens at TG?

There is a certain temperature(different for each polymer) called the glass transition temperature, or Tg for short. When the polymer is cooled below this temperature, it becomes hard and brittle, like glass. Some polymers are used above their glass transition temperatures, and some are used below.

Does crystallinity affect TG?

At low degrees of crystallinity, Tg of amorphous domains slowly increases, and then increases much faster at high degrees of crystallinity.

What is the difference between TG and TM?

The terms TG (or Tg) and TM (or Tm) give two important parameters of polymers. These are temperatures at which the texture of polymer changes. These values are characteristic features of polymers. TG refers to the glass transition temperature whereas TM refers to the melting temperature.

Whats is TG?

Glass Transition Temperature (Tg) is the point at which a material alters state – going from a glass-like rigid solid to a more flexible, rubbery compound. Tg is normally measured on a Differential Scanning Calorimeter (DSC) piece of whizzy equipment.

Which factor mostly affects the Tg of PVC?

Stronger intermolecular forces lead to a higher Tg. PVC has stronger intermolecular forces than polypropylene because of the dipole-dipole forces from the C-Cl bond.

What are the factors affecting TG?

Factors Affecting Tg

• Molecular Weight – In straight chain polymers, increase in MW leads to decrease in chain end concentration resulting in decreases free volume at end group region – and increase in Tg.
• Molecular Structure – Insertion of bulky, inflexible side group increases Tg of material due to decrease in mobility,

Why is steady state not equilibrium?

For an equilibrium, all concentrations are constant over time. For a steady-state, there is a net reaction, so some amounts change (the amount of source and sink), while at least one species – the one at steady state – has a constant concentration as long as the conditions of steady state prevail.

What is the steady state equilibrium?

A state of chemical equilibrium is reached when the concentration of reactants and product are constant over time (Wikipedia). In contrast, steady state is when the state variables are constant over time while there is a flow through the system (Wikipedia). …

What is non equilibrium steady state?

Non-equilibrium thermodynamics is a work in progress, not an established edifice. One problem of interest is the thermodynamic study of non-equilibrium steady states, in which entropy production and some flows are non-zero, but there is no time variation of physical variables.

What is the difference between equilibrium and non-equilibrium cooling?

In equilibrium cooling, the cooling rate is so slow, whereas, non-equilibrium cooling process has a higher cooling rate.

What is non-equilibrium flow?

Chemical and thermodynamic nonequilibrium conditions are often coupled to each other. Under nonequilibrium, the internal temperature, if exists, does not correspond to the kinetic energy of translational motion of particles.

What does thermodynamic equilibrium mean?

Thermodynamic equilibrium, condition or state of a thermodynamic system, the properties of which do not change with time and that can be changed to another condition only at the expense of effects on other systems.

What is a quasi equilibrium process?

In thermodynamics, a quasi-static process (also known as quasi-equilibrium, from the Latin quasi, meaning ‘as if’), is a thermodynamic process that happens slowly enough for the system to remain in internal equilibrium. Any reversible process is a quasi-static one.

What is a non equilibrium system chemistry?

Irreversible, non-equilibrium reactions are characterised by a negative change in enthalpy and positive change in entropy. In other words, these formation of products release heat (exothermic) and increases the disorder-ness of the system.

Is equilibrium a dynamic?

Dynamic equilibrium only occurs in reversible reactions, and it’s when the rate of the forward reaction is equal to the rate of the reverse reaction. These equations are dynamic because the forward and reverse reactions are still occurring, but the two rates are equal and unchanging, so they’re also at equilibrium.

Are all combustion reactions irreversible?

Combustion reactions are generally irreversible. In a complete combustion reaction, fuel and oxygen are the reactants and the products are carbon dioxide and water. These two products cannot react to reform the fuel and oxygen, so the reaction is irreversible.

Is photosynthesis a spontaneous process?

Photosynthesis in its entirety is an anabolic, nonspontaneous (endergonic) process driven by energy captured from sunlight.